Method and apparatus for manufacturing twisted fiber strands from staple fibers,especially from glass staple fibers



Feb. 4, 1969 w H LLER' ET AL 3,425,204

METHOD AND APPARATUS FOR MANUFACTURING TWISTED FIBER swamps FROM STAPLE FIBERS, ESPECIALLY FROM GLASS STAPLE FIBERS Filed Sept. 15, 1966 INVENTORS 00/" J MAX-4- Z'M United States Patent G 44,694 U.S. Cl. 5758.89

25 Claims Int. Cl. D01h 7/00; D02g 3/02 ABSTRACT OF THE DISCLOSURE A method and apparatus for manufacturing twisted fiber strands in which a stream of air with fibers, especially glass fibers, suspended therein is guided in substantially tangential direction along a stationary surface of circular cross-section and wherein the fibers are withdrawn along the axis of this surface and through a tube rotating at high speed about its axis so :as to rotate the air surrounding the strand of fibers in the tube to thereby twist at least the outer layer of the strand about the strand axis.

The present invention relates to a method and apparatus for manufacturing twisted fiber strands from staple fibers, especially from glass staple fibers.

In manufacturing slightly twisted strands from glass staple fibers, machines of known construction are used in which glass filaments produced from thin streams of molten glass are withdrawn by means of a fast rotating drum and, before passing over the whole circumference of the drum, are divided into fibers of irregular staple length by :a doctor blade engaging the outer drum surface, and guided by this blade and the air stream produced by the fast rotating drum into a substantially cylindrical or conical member or spinning tube having an axis parallel to the drum axis.

The fibers are gathered in the aforementioned member to form a strand which is withdrawn in axial direction from the member whereby the strand is slightly rotated and the number of twists will depend on the time the fibers remain in the aforementioned member, that is on the withdrawal speed of the strand from the member. In other words, the tensile strength of the strand, respectively the compactness of the strand structure, will depend on the withdrawal speed.

Machines of the aforementioned type are also known in which the filaments withdrawn by a single drum are guided into a plurality of correspondingly shorter spinning tubes so that a relatively large mass of fibers may be simultaneously formed into a plurality of fiber strands. Due to the shorter spinning tubes the fibers will remain a short time therein and leave the tubes twisted to a lesser degree.

These known methods and apparatus are suflicient as long as the strand produced in the aforementioned apparatus is wound up with relatively low speed, for instance with a speed of 250 meters per minute, and when for weaving the thus produced strands slowly operating looms with shuttles are used.

Modern manufacturing methods require, however, a greater withdrawal speed, from about 500 meters per minute and more, and in addition, in many cases a tighter twisted strand without [any loose surface fibers is required for the further processing of the strand.

Various suggestions have already been made in order 3,425,204 Patented Feb. 4, 1969 to increase the tensile strength of the strand or to improve unwinding of the strand from a spool. For instance, it has been suggested to use conical spools instead of cylindrical spools which improves unwinding even with a small spool diameter; however, this required respooling of the strand onto the conical spool, that is an additional process step, which evidently detrimentally affected production cost.

It has also been suggested to wind a continuous glass filament about the strand of fibers so as to produce a more compact strand structure or to increase the tensile strength of the fiber strand by embedding therein a continuous glass filament extending in axial direction of the strand.

These two methods require also additional production steps, increasing the cost of the produced strand and in addition, the continuous filament detrimentally affected the elasticity or extensability of the thus-produced strand.

It has also been suggested to improve the tensile strength of the strand, respectively to provide the strand with a smoother surface and therefore a more compact structure, by adding a lubricating substance, that is an oily substance, to the fibers which reduces the friction between the glass fibers so that even during slightly twisting the same a more compact structure is obtained. Such lubricating material has been added in the amount of 0.5 to 2% of the weight of the fibers.

However, since addition of lubricant material in greater amounts to the fibers considenably reduces the absorption capacity and impregnating capacity of the strands produced by the fibers as well as that of fabrics produced from the strands, it is preferred to use only a minimum amount of such lubricating materials.

It is an object of the present invention to provide for a method of manufacturing twisted fiber strands from glass fibers in which the produced strand has a relatively great tensile strength and compact structure and in which the disadvantages of the various methods known in the art to produce such a strand are avoided.

It is an additional object of the present invention to provide for an apparatus for carrying out such a method.

With these objects in view, the method for manufacturing [a twisted fiber strand from glass fibers basically comprises the steps of guiding a stream of fibers along a surface of substantially circular cross section, withdrawing the fibers along the axis of said surface to form a strand of fibers, and rotating the air surrounding the strand at high speed about the strand axis so as to twist at least the outer layer of said strand about said axis.

The apparatus for carrying out the aforementioned method mainly comprises a hollow member of circular cross section, means for guiding staple fibers substantially parallel to each other and transverse to the axis of the member into the latter and for subjecting the same therein to a rotary motion substantially about the axis of the member, a tube coaxial with the member and extending with an end portion through an end wall thereof into the latter, means mounting the tube turnable about its axis, means for rotating the tube about its axis, and means for withdrawing a strand of fibers formed in the member in axial direction through the tube, which has an inner diameter greater than the outer diameter of the strand of fibers.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a schematic rear view of a known apparatus for manufacturing a fiber strand;

FIG. 2 is a partial sectional view of an apparatus according to the present invention drawn to a larger scale than FIG. 1, the portion shown in FIG. 2 is a portion corresponding to the portion encompassed by the dashdotted circle II of FIG. 1, and it is to be understood that the apparatus of the present invention only partially shown in FIG. 2 includes otherwise the elements of the apapratus shown in FIG. 1; and

FIG. 3 is a perspective view of a modified component of the apparatus as shown in FIG. 2 and drawn to a further increased scale.

Referring now to the drawing, and more specifically to FIG. 1 of the same, in which an apparatus for forming slightly twisted fiber strands from glass filaments is schematically illustrated, it will be seen that the apapratlus mainly comprises a filament-producing device 1 which may include a container adapted to contain a mass of molten glass and provided at its bottom with a plurality of nozzles 2 through which thin streams of molten glass are discharged from the container, or a filament-producing device may comprise a plurality of glass rods arranged closely adjacent to each other, the bottom ends of which are subjected to heat and from which thin glass filaments are withdrawn in plastic state to form in either case after hardening a plurality of solid thin glass filaments 3. The filaments 3 are in actuality obviously produced in much greater numbers and arranged much closer to each other than schematically shown in FIG. 1. The filaments are engaged by the outer surface of a drum '4 rotating at high speed in the direction indicated by the arrow A whereby the filaments are withdrawn from the divec 1, 2 and drawn out to a desired thickness. By means of a doctor blade 5, engaging the drum surface, the filaments are lifted from the drum surface and divided into staple fibers of non-uniform length. The drum 4 is mounted in bearings 6 for rotation about its axis and is rotated by means not shown in FIG. 1 at high speed about its axis whereby the layer of air surrounding the outer drum surface is set in rotation and the thus produced wind feeds the fibers into a stationary cylindrical or conical hollow member or spinning tube 7 through an opening in the latter extending in longitudinal direction of the spinning tube in which a rotary motion is imparted to the fibers. The axis of the spinning tube is preferably parallel to the drum axis and the opening of the spinning tube is arranged adjacent to the doctor blade 5. A tube 9 extends coaxial with the spinning tube 7 through an end wall 8 of the latter and the continuously produced fiber whirl in the spinning tube is withdrawn in form of a fiber strand .10 from the latter through the tube 9, guided over a guide roll and finally wound up on a spool 11.

The schematically illustrated apparatus according to the prior art as shown in FIG. 1 is improved according to the present invention in that instead of a stationary tube 9 as shown in FIG. 1, the tube of the apparatus according to the present invention through which the fiber strand formed in the member 7 is withdrawn is mounted for rotation about its axis and driven at considerable speed about its axis. As schematically shown in the partial view of the apparatus according to the present invention illustrated in FIG. 2, the tube 12, corresponding to the tube 9 in FIG. 1, is mounted for rotation about its axis on ball bearings 13 and rotated about its axis by drive means 14, shown in FIG. 2 as a gear drive. Obviously, other drive means, for instance a belt drive, may be used for rotating the tube 12 about its axis. Due to the fast rotation of the tube 12, the air in the tube surrounding the strand of fibers passing therethrough is, due to the frictional engagement with the inner tube surface, also rotated so as to produce on the fiber strand passing therethrough a twisting action whereby the outer fibers of the strand are pressed onto the strand core and spirally wound about the same. The speed of rotation of the tube 12 is chosen in dependence on the speed of withdrawal of the fiber 7 strand through the tube and in experiments carried out by the inventor the fiber strand was withdrawn with a speed of 375 meters per minute and the tube 12 was rotated with 9000 revolutions per minute about its axis. Preferably, and depending on the desired structure of the strand, for each meter per minute of withdrawing speed, the tube is rotated with 5 to 30 revolutions per minute.

The rotation of the tube 12 may be carried out in the same or in the opposite direction in which the fibers rotate in the spinning tube 7 by the air whirl produced therein. Experiments have shown that it is advisable to rotate the tube I12 in the same direction as the fibers rotate in the member 7 when a fiber strand with a high tex-number is to be produced, for instance a tex-number 333, whereas for producing a fiber band with a low texnumber, for instance tex 200 or tex 100, the tube 12 is preferably rotated in a direction opposite to the direction of rotation of the air whirl in the member 7.

The relationship of the inner diameter of the tube 12 to the outer diameter of the fiber strand passing therethrough has also a considerable influence on the compactness of the structure of the fiber strand produced so that by a proper choice of this relationship it is possible to produce a more or less compacted fiber strand. Experiments have shown that even with relatively small number of revolutions of the tube 12 with a fiber strand of small tex-number, for instance tex 100, which for its production requires a very high withdrawal speed, a properly compacted strand structure can be obtained when the inner diameter of the tube 12 is held correspondingly small.

In addition a certain rotation is also imparted to the fiber strand and individual fibers projecting from the fiber strand are engaged by the inner surface of the tube and thereby wound about the strand. Experience has shown that the tensile strength of the fiber strand is thereby greatly increased and in actual experiments an increase of tensile strength of 50% and more has been ascertained.

In order to avoid ballooning of the rotating strand at the outer end of the withdrawal tube, a stationary guide tube 15 is preferably arranged coaxially with the tube 12 spaced a short distance from the outer end thereof through which the strand is guided after leaving the tube 12. The guide tube 15 may be provided with a short feed tube 16, extending transversely thereto and communicating with the interior thereof, for feeding binder or lubricating material into the guide tube 15, whereby such lubricating or binding material may be fed onto the rotating fiber strand passing through the guide tube.

A preferred embodiment of the withdrawal tube according to the present invention is shown in a further enlarged scale in the perspective view of FIG. 3. The withdrawal tube comprises a cylindrical tube portion 17 which is mounted for rotation about its axis on ball bearings or the like, as shown for the tube 12 in FIG. 2, and a conical end portion 18 which projects into the spinning tube 7 not shown in FIG. 3. The end face 19 of the conical end portion 18 is formed with slots 20 extending from the end face 19 into the portion 18 and which may be arranged in form of a cross as shown in FIG. 3. The slots 20 serve to feed fibers freely flying in the spinning tube 7 and which are not engaged by the forming fiber strand, for instance fibers which are introduced into the spinning tube in the region B, into the strand. For instance, fibers introduced into the spinning tube 7 in the direction of the arrows C or D will, when impinging on the conical end portion 18, be deflected by the same to slide on the outer surface thereof in direction of the arrow E and be engaged wither by the fiber cone 'F forming at the inlet end of the conical end portion 18 of by one of the slots 20 and thereby wound in spiral form about the forming fiber strand.

In order to introduce all fibers into the strand it has proven advantageous to provide an air stream which transports the fibers introduced in the aforementioned zone B toward the inlet end of the end portion 18 of the tube, which in the embodiment illustrated in FIG. 3 is accomplished by providing small openings 21 into the end wall 22 of the spinning tube 7 which may be fixed to the tube 17 for rotation therewith or which may be stationarily connected to the remainder of the spinning tube 7.

The compactness of the formed strand is influenced by the arrangement of the withdrawal tube relative to the spinning tube 7 and the compactness is increased the farther the withdrawal tube 12 extends into the spinning tube 7. For this reason the withdrawal tube 12 may, alone or together with its drive 14, be shifted in axial direction of the tube 12 towards the right or the left as indicated by the arrows G and H so that the tube 12 as shown in FIG. 2 or the tube 17 with the conical end portion 18 as shown in FIG. 3 extends to a greater or lesser degree into the spinning tube 7. In this case, the end wall 22 shown in FIG. 3 has of course to be fixedly connected to the remainder of the spinning tube. The axial adjustability of the withdrawal tube provides a simple means to compact the fiber strand to a greater or lesser degree.

The method and apparatus according to the present invention are used for producing a twisted fiber strand of increased tensile strength and compactness and the method and apparatus according to the present invention have proven especially advantageous if the amount of fibers introduced per time unit into the spinning tube is relatively great, respectively when the fiber strand is withdrawn at high speed from the spinning tube, or when the space for forming a strand from the whirling fibers is relatively small.

The above-described arrangement for forming a twisted fiber strand may be modified in various ways. For instance, the withdrawal tube may be formed slightly different from the forms as illustrated in FIGS. 2 and 3, for instance instead of a cone 18 other means may be provided to introduce free flying fibers into the strand, and for this purpose the portion of the withdrawal tube projecting into the spinning tube 7 may be provided on the circumference thereof with a plurality of openings communicating with the interior of the tube, or appropriate guide vanes may be provided on the spinning tube 7 projecting into the interior thereof. The withdrawal tube 12 may also have an inner diameter decreasing from the inner toward the outer end thereof and such decrease of the inner diameter may either be formed in steps or in a continuous manner. Furthermore, the withdrawal tube may also be formed from a plurality of coaxial sections rotated at different speeds, whereby the speed of successive sections preferably increases in direction of movement of the strand passing therethrough. To obtain such a result appropriate drives for the tube sections must be provided.

The method according to the present invention permits to vary the compactness, tensile strength, the absorbency and impregnation capacity of the produced strand within wide limits. The withdrawability of the strand from cylindrical spools is thereby greatly increased which is important for further processing of the strand at a high speed. Due to the improved withdrawal of the strand from a spool or bobbin on which it is wound the total amount of yarn wound on a bobbin may be increased from 1 kilogram to about 4 to 5 kilograms, which in turn reduces the necessary time for exchanging the bobbins during weaving to a fourth respectively to a fifth. In addition, the method of the present invention permits also the weaver to vary the structure, that is the compactness of the produced fabric without changing the spacings between the weft and warp threads. This permits also in a very simple manner to vary the possibility of the weft and warp threads to shift in the produced fa'bric relative to each other or to vary the absorbency, the impregnation capability and the stiffness of the produced fabric.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of methods and apparatus for manufacturing twisted fiber strands differing from the types described above.

While the invention has been illustrated and described as embodied in a method and apparatus for manufacturing twisted fiber strands, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readil adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A method of manufacturing twisted fiber strands, comprising, the steps of guiding a stream of air with fibers suspended therein along a stationary, a concave and continuous surface of circular cross-section in direction transverse to the axis of said surface; withdrawing the fibers along the axis of said surface to form a strand of fibers; and rotating the air surrounding said strand at high speed about the strand axis so as to twist at least the outer layer of said strand about said axis.

2. A method as set forth in claim 1, wherein said stream of fibers is guided in one direction about said surface and wherein the air surrounding the strand is rotated in the same direction.

3. A method as set forth in claim 1, wherein said stream of fibers is guided in one direction about said surface and wherein the air surrounding the strand is rotated in the opposite direction.

4. A method as set forth in claim 1, wherein the speed of rotation of the air surrounding the strand is increased in feeding direction of said strand.

5. A method as set forth in claim 1, wherein said strand is withdrawn through a tube extending along the axis of said surface and having a diameter greater than the strand and wherein said tube is rotated about its aixs.

6. A method as set forth in claim 5, wherein said strand is withdrawn at a speed of x meters per minute, and wherein the number of revolutions per minute of said tube is between 5x-30x, wherein x is a number greater than 250 meters per minute.

7. A method as set forth in claim 1, wherein the fibers are glass fibers.

8. Apparatus for manufacturing twisted fiber strands comprising, in combination, a stationary hollow member of substantially circular cross section; means for guiding staple fibers substantially parallel to each other and transverse to the axis of said member into the latter and for subjecting the same therein to a rotary motion substantially about the axis of said member; a tube coaxial with said member and extending with an end portion through an end wall of said member into the latter; means mounting said tube turnable about its axis relative to said stationary member; means cooperating with the tube for rotating the same about its axis relative to said stationary member and means for withdrawing a strand of fibers formed in said member in axial direction through said tube, said tube having an inner diameter greater than the outer diameter of said strand of fibers.

9. An apparatus as set forth in claim 8 and including mechanical means in the region of said end portion of said tube for picking up fibers flying freely in this region.

10. An apparatus as set forth in claim 9, wherein said means are provided on said end portion of said tube.

11. An apparatus as set forth in claim 10, wherein said end portion of said tube has an end face, and wherein said means comprise slots extending from said end face in said tube.

12. An apparatus as set forth in claim 8, wherein said end portion of said tube is conical, having its smallest diameter at its inner free end thereof.

13. An apparatus as set forth in claim 12, wherein the end face of said conical end portion of the tube is provided with slots extending from said end face into said conical end portion.

14. An apparatus as set forth in claim 8, and including a plurality of guide vanes on said member in the region about said end portion of said tube for guiding fibers flying freely in the interior of said member towards the free end of said tube end portion.

'15. An apparatus as set forth in claim 8, wherein said end wall of said cylindrical member is formed with openings therethrough.

16. An apparatus as set forth in claim 8, wherein the inner diameter of said tube decreases from the inner end in said member towards the outer end thereof.

17. An apparatus as set forth in claim 16, wherein said inner diameter decreases in steps.

18. An apparatus as set forth in claim 17, wherein said inner diameter decreases in a continuous manner.

19. An apparatus as set forth in claim 8, wherein said tube comprises a plurality of axially aligned sections, and wherein said drive means are constructed and arranged to drive said tube sections with different speeds.

20. An apparatus as set forth in claim 19, wherein said drive means are constructed and arranged to drive said tube sections with speed increasing in direction of movement of said strand through said tube sections.

21. An apparatus as set forth in claim 8, and including a stationary guide tube axially aligned with said rotating tube and arranged closely adjacent to the outer end of the latter.

22. An apparatus as set forth in claim 21, and including means for feeding material into said guide tube for treating the strand as it passes therethrough.

23. An apparatus as set forth in claim 8, wherein said end wall of said member is fixed to said tube for rotation therewith.

24. An apparatus as set forth in claim 23, wherein said end wall is formed with a plurality of small openings therethrough.

25. An apparatus as set forth in claim 8, wherein the position of the tube is adjustable in axial direction relative to said stationary member so that end portion of said tube may extend to a greater or lesser degree into said member.

References Cited UNITED STATES PATENTS 2,700,866 2/1955 Strang. 2,808,697 10/1957 Williams 5758.95 2,911,783 11/1959 Gotzfried 5758.95 3,330,008 7/1967 Schuller 5758.91

FOREIGN PATENTS 536,990 2/195'7 Canada.

STANLEY N. GILREATH, Primary Examiner.

WERNER H. SCHROEDER, Assistant Examiner.

US. Cl. X.R. 57-157 

